OBJECTIVE: To
describe methods and initial findings of a surveillance system of risk factors
for chronic non-communicable diseases (CNCDs) based on telephone interviews.METHODS: Interviews undertaken in a random sample of the adult population
of the Municipality of São Paulo living in households with telephone.
Sampling was done in two steps and included the random selection of households
and the random selection of the household member to be interviewed. The system's
questionnaire investigated demographic and socioeconomic characteristics, food
consumption and physical activity patterns, smoking, consumption of alcoholic
beverages, recalled weight and height and reported medical diagnoses of hypertension
and diabetes, among other topics. Prevalence estimates of selected risk factors
for CNCDs were calculated for the adult population with telephone and for the
city's entire adult population. In this last case, we applied sample weighting
factors that took into account demographic and socioeconomic differences between
the adult population with telephone and the entire adult population of the municipality.RESULTS: Strong differences between sexes were found for most risk factors:
low consumption of fruit and vegetables, high consumption of alcohol and overweight
were more frequent among men while sedentary lifestyle and hypertension were
more frequent among women. Additional possibilities of stratification of risk
factor prevalences allowed by the surveillance system are illustrated using
age groups, schooling, and place of residence in the city.CONCLUSIONS: System performance was considered as good and was better
than the performance observed in similar systems operating in developed countries
when evaluated with basis on the representativeness and reliability of the estimates
and on costs. The cost per concluded interview was eight times lower than the
cost usually seen in similar systems in developed countries and four to eight
times lower than the cost of traditional household surveys undertaken in the
city of Sao Paulo.

Chronic non-communicable diseases (CNCDs) are extremely
relevant to the current health profile of human populations. This
is true for both the global population as a whole and the
Brazilian population in particular. The World Health Organization
(WHO) estimates that CNDCs already account for 58.5% of all
deaths worldwide and for 45.9% of the global disease burden,
expressed as lost years of healthy life.25 In Brazil,
it is estimated that cardiovascular diseases and neoplasias alone
account for almost one-half of all deaths by known
causes.6 Mortality time series, available for the
Brazilian capitals, indicate that the proportion of deaths due to
CNCDs more than tripled between the 1930's and
1990's.1

Cross-sectional and prospective epidemiological studies have
provided exhaustive proof of the association between several of
the major CNCDs (cardiovascular diseases, respiratory diseases,
diabetes, and certain types of cancer) and a relatively small
group of risk factors, noteworthy among which are smoking,
excessive alcohol consumption, overweight, arterial hypertension,
hypercholesterolemia, low fruit and vegetable consumption, and
physical inactivity.23 According to recent WHO
estimates, these seven risk factors are part of the list of
fourteen factors most relevant to the total global disease
burden. In countries like Brazil, these same risk factors are
part of the list of nine factors that most cause death and
disease among the population.22

Although potentially relevant to the definition of the
epidemiological profile of the Brazilian population, and, more
importantly, potentially preventable, risk factors for CNCDs are
not being adequately monitored. Household surveys on the
occurrence of health and nutrition conditions in the Brazilian
population have shown a sharp increase in obesity , especially in
poorer socioeconomic strata.11,13,15 Notwithstanding,
in light of the wide intervals separating these surveys (10-15
years) and of the impossibility of sorting data by state and
municipality, one cannot consider the issue of obesity in this
country as being adequately monitored. Knowledge of the time
trends of food consumption and of physical activity patterns is
even more scarce. Regarding the former, periodical information
are restricted to the trends in metropolitan areas, estimated
based on surveys of family budgets, which refer to the purchase
of food by families rather than to the actual consumption pattern
of individuals.9,14 As to the latter, a single
recorded household survey estimated the frequency of physical
activities during leisure time in the Northeast and Southeast
Regions of Brazil in 1996/97.16 Anyhow, data in both
cases point towards patterns of food consumption and physical
activity that greatly favor the occurrence of CNCDs. The most
recent estimates on the consumption of cigarettes and alcohol in
the country date from 15 years ago and also cannot be sorted by
state and municipality,7 whereas estimates of the
prevalence of arterial hypertension and hypercholesterolemia are
mostly punctual, and refer to very specific
populations.2

One of the explanations proposed for the dissatisfactory
monitoring of risk factors for CNCDs in the Brazilian population
is that household surveys, the major instrument employed in the
country for generating monitoring information, are operationally
complex, costly, and generally involve long stretches of time
between study planning and the publication of results. Such
conditions render household surveys inadequate as the single or
main source of information for monitoring systems, particularly
for state or municipal ones.

The system presented
in the present paper is a potentially simple, inexpensive, and agile system
for monitoring risk factors for CNCDs. This system is based essentially on annual
surveys carried out by means of telephone interviews with probabilistic samples
of the population living in homes with fixed telephone lines. Similar systems
are being used successfully3
in populations in which telephone services reach the great majority of residences,17
a scenario projected for most Brazilian cities in the relatively near future.4

Below we describe the methods and initial results of the
pioneer experience in Brazil of implementing a CNCD risk factor
monitoring system based on telephone interviews. Subsequent
papers will report on additional results and focus on aspects
related to system reliability and validation.

METHODS

In 2003, in the Municipality of Sao Paulo, we implemented a
system for monitoring risk factors for CNCDs through telephone
interviews (SIMTEL/MSP). The sampling procedures employed by the
SIMTEL/MSP were aimed at obtaining a probabilistic sample of the
population aged 18 years or older, living in households in the
city of Sao Paulo with at least one telephone line in 2003. We
established the minimum number of subjects to be studied by the
system at 2,000, which would allow us to estimate the frequency
of any risk factor in the studied population with a 95%
confidence coefficient and a maximum error of about two
percentage points. Maximum errors of about three percentage
points would be expected for gender-specific estimates, assuming
45% of men and 55% of women in the final sample.20

The first stage
of sampling was carried out in October 2003 and consisted of drawing 7,000 telephone
lines from the electronic registry of residential fixed telephone lines in the
municipality of Sao Paulo. This registry5
comprised 2,915,860 lines. A telephone company staff member, who was supervised
by one of the authors, carried out the draw. The draw, stratified and systematic,
took into account the five strata into which the registry was divided, corresponding
to the Central, North, South, East, and West Regions of the city. The same sampling
fraction was maintained in all regions (1/416). The 7,000 lines drawn were then
redrawn and divided into twenty replicates of 350 lines ordered from 1 to 20,
each replicate reproducing the proportion of lines according to city region.
We divided the total sample into replicates due to difficulties in estimating
the proportion of lines in the registry eligible for the system (active residential
lines) and, therefore, the total number of lines that should be drawn in order
to reach 2,000 interviews.

The second stage
of the sampling process was the selection of individuals  one per telephone
line  to be interviewed by the system. This stage, carried out in parallel
with the interviews  between 15 October and 31 December 2003 , involved
prior identification, among the lines drawn, of lines that were both residential
and active (eligible lines) and the obtainment of the consent of users of these
lines to participate in the system. To this end, we placed calls to the telephone
lines included in the replicates drawn from one to nine, that is, to 3,150 lines
(9x359). We considered as ineligible for participation in the system lines that
were out of service (n=235), commercial lines (n=138) or unexisting phone number
(n=109) , and lines for which we could not obtain an answer after ten calls
placed on different days and at different times, including weekends and evenings,
and that probably corresponded to closed residences (n=163), which resulted
in a total 2,505 eligible telephone lines, or roughly 80% of the total initially
drawn. Refusals to participate in the system were observed in 157 of the 2,505
eligible lines (6.3%). Another 37 lines remained busy (n=4) or were answered
by fax (n=15) or answer machines (n=18) after ten calls placed on different
days and times, including weekends and evenings. We were thus able to draw individual
subjects in 2,311 (92.3%) of the 2,505 eligible lines. This draw was done based
on the a list of all individuals living in the residence aged at least 18 years,
ordered ascendantly by age, and by reference to random number sequences corresponding
to the number of adults living in the household. Thus, for example, in households
with four adults, we referred to a random sequence of numbers 1, 2, 3, and 4
(e.g., 3,1,2,4,2,3,1,4,4,1,2,3 ), selecting for the interview the
number immediately following the one selected for the previous interview.

The SIMTEL/MSP questionnaire comprised 89 short, simple
questions, the great majority of which included preestablished
answer categories. Many questions in the questionnaires were
linked and, depending on the answers obtained, many questions
were skipped, thus reducing the actual number of questions by up
to 40%. The questionnaire was constructed so as to allow for the
telephone interviews to be carried out with the aid of a
computer, that is, questions were read directly from a computer
screen and answers were entered digitally (using the keyboard or
mouse), directly and immediately. The questionnaire, built in
'fox-pro' language, allows for the automatic skipping of
non-applicable questions based on prior answers, and provides
direct and continuous feeding to a 'd-base' format data bank.
After obtaining the subject's agreement, interviews were recorded
and saved to electronic media for subsequent quality control.

The questionnaire addressed especially: a) individual
demographic and socioeconomic characteristics (age, gender,
marital status, ethnicity, schooling, occupation, neighbourhood
of residence, number of persons and rooms in the household,
number of adults, and number of telephone lines); b) certain
characteristics of consumption and physical activity patterns
associated to the occurrence of CNCDs (including frequency of
consumption of fruit and vegetables and of foods rich in
saturated fats, frequency and duration of physical exercise, and
habit of watching television); c) characteristics related to body
composition (recalled weight and height); d) frequency of
consumption of cigarettes and alcoholic beverages; and e)
self-rated health status and reference to prior medical diagnosis
of arterial hypertension, high cholesterol levels, and diabetes.
The construction of the questionnaire took into account models of
simplified questionnaires used by systems for the monitoring of
CNCD risk factors17,21 and the experience accumulated
in a number of surveys of health and nutrition carried out in
Brazil. Preliminary versions of the questionnaire used in the
system were tested during the two weeks preceding the beginning
of interviews.

System operation and performance

The SIMTEL/MSP was operated by a technical team including one
interview scheduler, two interviewers, one coordinator, and two
coordination assistants. Overall, the system operated for a
period of three months (1 October to 31 December 2003), including
two weeks dedicated to training and pre-testing the instruments
used for data collection.

The interview scheduler placed initial telephone calls to all
the drawn lines, repeated these calls in case of failure (at
least ten times), confirmed whether the line at hand was an
active residential line, explained to this person (if aged 16
years or older) the characteristics and goals of the monitoring
system, requested the person's consent to participate in the
study, listed the adults (= 18 years) living in the household in
ascending order of age, selected the subject to be interviewed
from this list according to the random number sequences, and
recorded the best days and times for carrying out the telephone
interview. In the three months during which the system operated,
the scheduler placed a total 8,234 calls to the 3,150 selected
lines, a mean 2.61 calls per line. As we saw above, these calls
resulted in 2,505 eligible lines and in the selection of 2,311
subjects to be interviewed.

The two interviewers placed telephone calls to the selected
subjects, repeated the explanations regarding the system,
obtained subject's consent to be interviewed, and administered
the questionnaire, recording all the answers obtained directly
into the computer. The subjects selected for the interview were
called at the date and time suggested by the household member who
answered the initial call and, in case of failure, were called at
least ten times at different times and days, including weekends.
In the three months of system operation, the two interviewers
placed a total 5,967 calls to the 2,311 subjects selected, which
corresponded to a mean 2.58 calls placed per selected line. These
calls resulted in 2,122 interviews, or 91.8% of all interviews
programmed. Refusals accounted for the failure to carry out 5.8%
of the programmed interviews, and in the remaining cases (2.3%),
interviews were not carried out due to lines that went out of
service or which were not answered even after ten calls.
Considering the total of 2,505 active residential lines drawn
from the telephone company registry, the final success rate
(identification and selection of interview subjects and
questionnaire administration) in the present study was 84.7%. The
proportion of lines whose users refused to participate in the
study was 11.7%, and the proportion of lines that could not be
contacted was 3.6%. The median duration of the interviews
administered was 9.3 (mean =9.9 minutes; standard deviation =3.4
minutes).

Finally, the study coordinator, aided by two assistants,
recruited and trained the remaining team members, prepared and
distributed work charts to the scheduler and interviewers,
reviewed recorded telephone interviews (the initial interview of
all interviewers plus a random sample of 20% of subsequent
interviews), indicated problems and failures in the voicing of
questions or in the recording of answers, indicated the need for
further telephone contact with the subject for the correction of
answers, periodically evaluated the consistency of the database
built based on the interviews, and produced simple tabulations of
the frequency and distribution of selected risk factors.

Data analysis

The selected SIMTEL/MSP indicators presented below include
behavioral variables (food consumption, physical activity,
smoking, and alcoholic beverage consumption), weight and height,
and reported prior medical diagnosis of arterial hypertension and
diabetes. The selection of indicators took into account the
importance of these indicators to the determination of the total
burden of disease in Brazil, as estimated by
WHO.22

We estimated the prevalence of these indicators for the
population of adults with a telephone line in the municipality
and for the total adult population of the municipality. In the
first case, we employed individual weighting factors
corresponding to the number of adults in the household multiplied
by the inverse of the number of telephone lines. In the second
case, we multiplied the individual weighting factor by an
additional factor that took into account the sociodemographic
differences between the population of adults with a telephone
line and the total adult population of the municipality. In order
to obtain this additional weighting factor, the population with a
telephone line (studied by the monitoring system and already
incorporating the weighting factor based on the number of adults
and telephone lines in each household) was compared to a sample
of the population of the municipality taken from the latest
demographic census (10% of households studied in 2000). This
comparison was based on the stratification of both samples
according to male and female gender, six age groups (18-24,
25-34, 35-44, 45-54, 55-64, and 65 years and older), and four
levels of schooling (0-4, 5-8, 9-11, and 12 or more years of
schooling). We then calculated, for each of the 48 strata, the
ratio observed between the frequency of the stratum in the census
sample and the frequency of the same stratum in the sample from
the monitoring system. We used this ratio as the additional
weighting factor that, when applied to the individuals of each
stratum, corrected an eventual under or overrepresentation of men
or women, age groups, or social strata in the sample of adults
studied by the monitoring system vis-à-vis the
representation of the same strata in the total adult population
of the municipality.

The prevalences of the selected indicators, adjusted to
represent the total adult population of the Municipality of Sao
Paulo, were calculated separately, with 95% confidence intervals,
for men and women. In addition, as an illustration of the
possibilities of stratification of the estimates provided by the
system, we present prevalence estimates according to the age
group and schooling level of subjects. Statistical analyses of
the association between risk factors and stratification variables
were performed using a statistical test based on the chi-squared
distribution. Data processing and statistical analyses were
carried out using Epi Info version 6.1 software, employing the
'csample' functions, that compute proportions with confidence
intervals taking into account the complex nature of sampling (use
of strata and weighting factors).6

Ethical aspects

Since interviews were conducted by telephone, free informed
consent forms were replaced by verbal consent obtained from
subjects during the telephone contacts. During these contacts, we
made clear that the data obtained would be used only for research
purposes and for the implementation of a municipal system for the
monitoring of risk factors for chronic non-transmissible
diseases. We also informed subjects of the possibility of
refraining form participation in the study at any moment during
the interview, of the inexistence of risk or of additional health
hazards, and of the guarantee that all information provided were
confidential. We provided a telephone number for the resolution
of any doubts concerning the project. This research project was
approved by the Ethics Committee of the School of Public Health
of the University of Sao Paulo .

RESULTS

Table
1 compares sociodemographic characteristics of the sample of the population
of adults with telephone line studied by the SIMTEL/MSP in 2003, with those
of the total adult population of the municipality, studied by the 2000 demographic
census. The population studied by the monitoring system has a greater proportion
of women (60.6% versus 53.5% in the census), a lesser proportion of youths between
ages 18 and 24 years (14.9% versus 19.8% in the census), and greater proportion
of subjects with nine or more years of schooling (64.2% versus 45.2% in the
census). Mean age and schooling in the studied population were 41.2 and 9.4
years, respectively, whereas the corresponding values for the total adult population
in the municipality were 39.6 and 8.1 years.

Table
2 presents SIMTEL/MSP estimates for the prevalence of selected risk factors.
The table presents estimates referent to the population of adults with telephone
lines and to the entire adult population of the municipality. It should be noted
that differences between the two estimates are relatively small and non-systematic:
in most cases, absolute differences do not exceed two percentage points, above
or below, and relative differences are always below 10%.

Table
3 presents SIMTEL/MSP estimates for the male and female adult populations
of the Municipality of Sao Paulo. Substantial differences between the genders
are observed with respect to the frequency of most risk factors studied. Significantly
more frequent among men are the insufficient consumption of fruit and vegetables,
excessive alcohol consumption, and overweight, whereas among women sedentary
lifestyle and hypertension are significantly more frequent.

Figures
1 and 2 illustrate further stratification options made
possible by the monitoring system, involving the age group and schooling of
the interviewed subjects. Figure 1 makes evident two relevant
risk factors for the male population of the Municipality of Sao Paulo: 1) after
age 50 years the frequency of former smokers is substantially higher than that
of current smokers; and 2) beginning to smoke seems to have declined substantially
in the last decades  roughly 70% of subjects aged 45 years or older (born,
therefore, before 1959) are smokers or former smokers, whereas only 32.8% of
subjects in the 18-24 years age group (born after 1979) are in the same situation.
Figure 2 indicates that sedentary lifestyle and obesity
tend to be more frequent among women with less schooling.

DISCUSSION

The discussion of the present article shall focus mainly on
two aspects that are crucial to monitoring systems based on
telephone interviewing: the representativity of the estimates and
the cost of the system. We used as a general reference for this
evaluation, whenever possible, the system of monitoring by
telephone interview used in the United States, the 'Behavioral
Risk Factor Surveillance System' (BRFSS). The BRFSS, created by
the US Centers for Disease Control and Prevention in 1981, is the
oldest and largest telephone monitoring system in the world. It
was implemented initially in 29 US states and, since 1994, works
regularly in all 50 states, in the District of Columbia, and in
the three US federal territories. Comparable to the system tested
in Sao Paulo, the BRFSS interviews probabilistic samples of
subjects 18 years or older with telephone lines in their
household employing questionnaires that address risk or
protective factors for CNCDs, including food consumption and
physical activity patterns, smoking and alcohol consumption,
recalled weight and height, and reported previous medical
diagnosis of arterial hypertension, hypercholesterolemia, and
diabetes, among other variables.3

An analysis of the representativeness of the sample of
subjects studied by a monitoring system based on telephone
interviews must take into consideration how well this sample
represents the group of individuals that have a telephone and how
well this same sample represents the entire population one wishes
to monitor. In the first case, three aspects must be considered:
the quality of the telephone registry used for drawing
residential lines, the adequacy of the sampling system employed
in the selection of telephone lines and users to be interviewed,
and, finally, the proportion of interviews completed in relation
to the total interviews programmed or predicted. In the second
case, it is also important to evaluate the degree of coverage of
telephone services in the population to be monitored and, in case
of non-universal coverage, the differences between individuals
living in households with and without telephone. We shall examine
each of these aspects below.

The telephone registry
used by the SIMTEL/MSP seems to be virtually universal, given that the proportion
of households with telephone service calculated based on this registry approaches
the coverage calculated based on household surveys. Considering the number of
lines in the 2003 registry (2,915,860 lines), subtracting from this number the
percentage of commercial lines (4.4%), and also considering the mean number
of lines per household (1,08), we arrive at a total of 2,581,076 households
with telephone service, which would cover 84.9% of permanent households estimated
for the same year (2003) in the Municipality of Sao Paulo (3,040,047 according
to the Fundação Sistema Estadual de Análise de Dados
 Seade).6 We arrive
at similar levels coverage if we base our calculations on the proportion of
households in the Municipality of Sao Paulo with at least one telephone line
in the year 2000 (67% according to Census data, processed by us) and on an expansion
in coverage of about 10% per year in the 2000-2003 period (projection based
on the evolution of fixed telephone coverage in the Southeast Region of Brazil
between 1999 and 2001).7
It is assumed that the telephone registries used by the BRFSS system include
a large share of the universe of residential telephone lines, even though the
registries fail to distinguish between residential and other lines in a number
of states.17

The availability
of a computerized registry, stratified by area of residence and specific for
residential telephone lines, allowed the use of systematic sampling by strata,
which is a fairly simple, traditional and reliable sampling procedure for the
selection of telephone lines.18 In order to draw the telephone user
to be interviewed, an equally simple and reliable procedure selection
based on random number lists  was employed.8 The American BRFSS
employs much more complex sampling systems due to the lack of a registry specific
for residential telephone lines. These procedures include a prior stage in which
area codes are drawn for a study of the proportion of residential lines in each
area code, and codes with greater potential for containing residential lines
are selected. In addition to a greater number of telephone calls, these procedures
also require the use of additional weighting factors in order not to compromise
the final representativeness of the sample obtained.19 In its early
years, the BRFSS selected for the interview the subject whose birthday was closest
to the date of the interview, but this procedure has recently been replaced
by the use of random number sequences.17 During the pre-testing of
the system implemented in Sao Paulo, we observed that the selection procedure
based on birthdays took an excessive amount of time and was not always properly
understood by the respondent.

The proportion of completed interviews in relation to the
total interviews predicted in the SIMTEL/MSP was 84.7%. This
success rate is similar to those obtained in household surveys
carried out in the 1980's and 90's in the Municipality of Sao
Paulo10,12 and higher than the success rate obtained
in different US states by the BRFSS system (median success rate
of 56.7% in 1999, ranging from 38.4% to 83.9%). The so called
'cooperation rate' (the proportion of interviews completed over
the proportion of interviews completed plus refusals) was equally
higher in the SIMTEL/MSP: 88.0%, versus 68.4% in the
BRFSS.4

Therefore we conclude
that the sample interviewed by the SIMTEL/MSP represents the population of the
Municipality of Sao Paulo with telephone. Regarding the representativeness of
the sample in relation to the entire population, as we have seen, one must consider
the coverage of telephone services in the municipality and the differences between
the population with and without telephone. In 2003, the proportion of households
with telephone in the municipality, according to the estimates already mentioned,
was of approximately 85%; a high, albeit far from universal, coverage. The differences
between the population with and without telephone in the municipality cannot
be determined directly, given that the most recent data available for such a
comparison date from the year 2000, when the coverage of telephone services
in the municipality was substantially lower than in 2003. Notwithstanding, a
comparison between the distributions with respect to schooling in the sample
studied by the SIMTEL/MSP and in the sample of the total adult population of
the municipality suggests substantial  though not surprising  socioeconomic
disadvantages to the population without telephone (Table 1).
Differences between the two samples were also found in terms of gender and age,
the monitoring system sample showing lesser proportions of males and of individuals
aged 18-24 years than those projected by the census. Such differences, however,
were due especially to the greater failure rates in the interviews with men
and, generally speaking, with very young subjects. The BRFSS does not face problems
related to the telephone coverage given the universal coverage in all American
states. Nevertheless, higher failure rates in interviews with men and youngsters
in general determine representativeness issues in terms of gender and age very
similar to those observed in the Municipality of Sao Paulo. Thus, between 1981
and 1987, the proportion of men in the BRFSS sample ranged from 40% to 42% and
the proportion of individuals aged 18-24 years form 11% to 14%, while the same
proportions in the 1980 American demographic census were, respectively, 48%
and 19%.20 In the SIMTEL/MSP sample, the proportion of males was
39.9% and that of youngsters, 14.2%, versus 46.6% and 19.8%, respectively, in
the 2000 demographic census.

In order to extend the representativeness of the monitoring
system sample to the entire adult population of the Municipality
of Sao Paulo we developed adjustment factors that simulate, in
the sample, the structure in terms of gender, age group, and
schooling observed in the entire adult population in the year
2000. These factors, when applied to the sample of the system,
produce estimates that would be observed if the sociodemographic
structure of this sample were the same as that of the entire
population. An analogous procedure is adopted by the BRFSS in
order to obtain estimates extendable to the entire US adult
population.17 In addition to making estimates closer
to those that would be obtained in case the total population of
the municipality could be studied directly, the use of adjustment
factors also allows us to control any eventual changes that may
occur in the structure of the monitoring system sample from year
to year. Such possibility is especially important in our case,
since changes in the structure of the population covered by
telephone services are likely to occur on a short term basis,
given the expansion that is still likely to occur in the coverage
of the telephone system in the Municipality of Sao Paulo (and in
other Brazilian cities).

The global cost
of the SIMTEL/MSP involved basically four expense elements: 1) expenses related
to physical installations and equipment (telephones, computers, software for
recording interviews and for online data entry, among others); 2) expenses related
to the working time of the researchers and technicians that designed the system,
including sampling procedures, questionnaire elaboration and the formulation
of indicators; 3) payment of the technical team (coordinator, two assistants,
and two interviewers); and 4) cost of telephone calls. The two first elements
of the expense are hard to quantify, since their cost was absorbed by the institution
(NUPENS/USP) that tested the system. In any case, equipment and system design
tend to represent a small share of the total cost of the system, since these
expenses are incurred in only once, and are therefore diluted throughout the
entire period of system operation. The monthly earnings of the project team
(R$700.008 for each interviewer
and assistant and R$1,500.00 for the coordinator) amounted to R$6,201.60, or
R$18,604.80 for the three months of operation, already including taxes and labor
duties. The cost of telephone calls and of the monthly fees of the three telephone
lines used amounted to R$4,530.80, taxes included. Thus the variable cost of
the system amounted to R$23,135.60, or R$10.90 per completed interview.

Higher per-interview costs are usually observed in household
surveys. The authors' experience in other household health and
nutrition surveys carried out in the Municipality of Sao Paulo
indicated mean costs per completed interview between R$50,00 and
R$100,00, depending on the characteristics of the interview. The
mean cost of the telephone interviews carried out in the American
BRFSS system is estimated at 25-30 US dollars, (roughly 90.00
Brazilian Reais), two to five times lower then the mean cost of
household interviews conducted in the United States.17
In addition to being relatively inexpensive, the SIMTEL/MSP
proved extremely agile: the entire process of sample selection,
scheduling, and interviewing was completed in three months, a
preliminary report was produced 30 days after the completion of
the last interview, and a full report was completed after 120
days. We wish to highlight that, although the SIMTEL/MSP operated
for three months, it would be equally possible to extend system
operation to twelve months, so as to make system operation
continuous, as in the American BRFSS system.

The present study showed that the system of monitoring of risk
factors for CNCDs based on telephone interviews is capable of
reaching good performance in Brazilian urban areas similar to Sao
Paulo, be it in terms of sample representativeness, be it in
terms of the cost and agility of the system. Further studies must
focus on aspects related to the reliability and validation of
monitoring systems such as the one implemented in the
Municipality of Sao Paulo.

ACNOWLEDGEMENTS

We would like to
thank the local telephone company  Telecomunicações de
São Paulo S/A (Telesp)  for its help with drawing the sample
of residential telephone lines; Silvio Fernando Barbieri for his expertise in
the field of informatics; and Rosemary Sena Alves, Maria Gabriela da Cunha,
and Danira Martins Passos for the technical support in all stages of the project.